It could be piece that seals inside/outside air mix for recirculation or outside air. Mine only squeaks a little when it goes either to inside or outside. And it'* really not a squeak just a rubber on plastic noise.
The mix for air intake to the blower motor is half open to inside and outside (atleast on the auto climate control), then when you push inside or outside air on the control, then the "bowl like" plastic piece seals off the other intake. That seal could be the noise, but why is it doing it every 15-30 seconds.... good question..
Originally Posted by BillBoost37
Ford is self induced pain and suffering. Doesn't count.